LTE frequency channel avoidance

ABSTRACT

A method of reducing interference to reception of streams of television content received at a television receiver in which each of the streams of television content are transmitted on one of a plurality of frequency channels in accordance with a channel map which defines on which of the plurality of frequency channels each stream of television content is transmitted and the interference being caused by a base station transmitting data to or receiving data from one or more mobile devices via radio communication signals in a vicinity of the television receiver. The method includes identifying the channel map and adapting a transmission of the radio communication signals between the base station and the one or more of mobile devices in accordance with the identified channel map to reduce interference at the television receiver.

TECHNICAL FIELD

The present invention relates to methods of reducing interference attelevision receivers produced by mobile communication systemstransmitting radio communication signals, and networks, systems andmobile communication base stations for reducing such interference.

BACKGROUND OF THE INVENTION

The UHF (Ultra High Frequency) radio band covers a range of frequenciesbetween 300 MHz to 3 GHz. Radio frequencies within the UHF band haveparticularly useful propagation and information bearing propertiestherefore many systems which rely on the communication of informationusing radio waves are designed to transmit and receive information onradio signals using the UHF radio band.

To ensure a fair and organised allocation of the UHF spectrum,regulatory bodies, such as the Office of Communications (OFCOM) in theUK and the Federal Communications Commission (FCC) in the United States,divide the UHF spectrum into different frequency bands and allocate eachband to a certain group of users and uses.

As time progresses, it becomes necessary for the regulatory bodies tore-organise the allocation of the UHF spectrum to accommodate newtechnologies which communicate using the UHF spectrum and to account forthe demise of older technologies which no longer justify a reservedsection of the spectrum. The task of reallocating bands of the UHFspectrum is not always made purely with technical considerations inmind.

For example, in the UK after 2012, radio transmitters broadcastingterrestrial television signals using the PAL (phase alternating line)analogue transmission mode on the so-called “800 MHz band” will ceasetransmitting. The “800 MHz band” refers to a range of frequenciesbetween 790 MHz and 862 MHz. These frequencies will be re-allocated byOFCOM for other uses such as so-called “fourth generation” mobilecommunications services. As a result mobile devices (such as mobiletelephones and other portable devices such as laptops, notebooks,camcorders, cameras with built in wireless communications functionality)can be expected to be deployed which transmit and receive radio signalson frequencies within the 800 MHz band. As fourth generation mobiledevices become more widespread, this may cause interference problemswith devices for receiving television signals such as televisions,personal video recorders (PVRs), set-top boxes and so on.

SUMMARY OF INVENTION

According to an aspect of the present invention there is provided amethod of reducing interference to the reception of streams oftelevision content received at a television receiver in which each ofthe streams of television content are transmitted on one of a pluralityof frequency channels in accordance with a channel map which defines onwhich of the plurality of frequency channels each stream of televisioncontent is transmitted and the interference being caused by a basestation transmitting data to or receiving data from one or more mobiledevices via radio communication signals in a vicinity of the televisionreceiver. The method comprises identifying the channel map and adaptinga transmission of the radio communication signals between the basestation and the one or more of mobile devices in accordance with theidentified channel map to reduce interference at the televisionreceiver.

The reallocation of certain frequency channels which are adjacent tofrequency channels used for terrestrial television broadcasts poses aproblem in that if the reallocated frequency channels are allocated foruse in mobile communications systems, the transmission of mobile radiocommunication signals on the reallocated frequency channels mayinterfere with the reception of television content broadcast on theadjacent frequency channels used for terrestrial television broadcasts.

The broadcasting of terrestrial television signals typically involvesdividing a geographical area into a number of television regions. Eachtelevision region is served by a television signal transmitter thattransmits a number of television content streams on a number ofdifferent frequency channels. The allocation of television contentstreams to a given frequency channel is defined in each televisionregion in accordance with a so-called channel map and the channel mapused varies between transmitters. In accordance with the presentinvention it has been recognised that this variation can be exploited byenabling mobile communication base stations to selectively adapt thetransmission of mobile radio communication signals based on the channelmap of a particular television region. This selective adaptation meansthat rather than completely suppressing interfering mobile radiocommunication signals across an entire network or simply tolerating anyinterference that arises, the otherwise unrelated information associatedwith channel maps can be used to selectively limit the transmission ofthe mobile radio communication signals such that interference is reducedwhilst maintaining the transmission of the mobile radio communicationsignals where possible.

In accordance with one example of the present invention, the radiocommunication signals are transmitted from the base station to the oneor more mobile devices via a downlink frequency channel and transmittedfrom the one or more mobile devices to the base station via an uplinkfrequency channel, the uplink frequency channel and the downlinkfrequency channel being divided into frequency sub-channels. The step ofadapting the transmission of the radio communication signals comprisesselectively limiting or blocking one or more of the frequencysub-channels of the uplink frequency channel and/or the downlinkfrequency channel.

In this example, the transmission of the radio communication signals isreadily and conveniently adapted by selectively limiting or blockingcertain uplink and downlink frequency sub-channels used when data istransmitted between the base station and mobile devices.

In accordance with another example of the present invention, identifyingthe channel map comprises identifying the channel map from data manuallyentered into a data store connected to the base station. In thisexample, location information can be conveniently provided to the basestation, for example when the base station is installed.

In accordance with another example of the invention, identifying thechannel map comprises identifying a location of the base station,determining from the location of the base station a television region inwhich the base station is located, and identifying the channel mapassociated with the television region. In accordance with this example,there is no requirement to manually enter the channel map, instead alocation of the base station is referenced with respect to a list oftelevision regions for which a list of channel maps is provided. Inaccordance with this example, each base station need only be providedwith a single look-up table containing all the relevant channel maps.

In accordance with a further example of the present invention,identifying the location of the base station comprises receivinglocation information from a positioning unit connected to the basestation or from one of the plurality of mobile devices.

In accordance with another example of the invention, informationcorresponding to which of the frequency sub-channels have beenselectively limited or blocked is transmitted to a second base station,wherein the second base station communicates data with a plurality ofmobile devices via radio communication signals in accordance with theadapted communication scheme. In accordance with this example, a firstbase station, for example a LTE macrocell base station can determine anappropriate adaptation to the transmission of radio communicationsignals on the frequency sub-channels which reduces interference to thereception of the television content. Information corresponding to thisadaptation can then be sent to another base station such as a femtocellbase station operating near the other base station. This allows thesecond base station (e.g. the femtocell base station) to transmit radiocommunication signals with a reduced likelihood of producinginterference without there being a need to undertake any determinationof how the transmission of the radio communication signals should beadapted.

In accordance with another aspect of the present invention, there isprovided a base station for transmitting data to and receiving data fromone or more mobile devices via radio communication signals. The basestation is operable to receive a channel map which defines on which of aplurality of frequency channels a plurality of streams of televisioncontent are transmitted and the base station is operable to adapt thetransmission of the radio communication signals from the base station tothe one or more mobile devices and to control the one or more mobiledevices to adapt a transmission of the radio communication signalstransmitted from the one or more mobile devices in accordance with thereceived channel map to reduce interference to the reception of thestreams of television content received at a television receiver in avicinity of the base station and the one or more mobile devices.

In accordance with another example of the invention, there is provided anetwork comprising a plurality of base stations as described above.

Various further aspects and features of the present invention aredefined in the claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described withreference to the accompanying drawings where like parts bear the samenumerical reference and in which:

FIG. 1 shows a table of frequency channels which are currently allocatedin the UK for the broadcast of terrestrial television signals;

FIG. 2 shows a schematic diagram providing a representation of aconventional television situated near a mobile device and a basestation;

FIG. 3 a shows a schematic diagram illustrating a first and secondversion of a potential allocation of the frequency spectrum in the 790to 862 MHz frequency band,

FIG. 3 b shows a schematic diagram illustrating a possibleimplementation of a UHF frequency band which could be used by a basestation and plurality of mobile devices;

FIG. 4 shows a schematic diagram illustrating the cellular structure ofa typical LTE mobile communication network;

FIG. 5 shows a map illustrating the distribution of digital televisiontransmitters throughout the UK;

FIG. 6 shows a schematic diagram illustrating part of a LTE mobilecommunication network;

FIG. 7 shows a schematic diagram providing an illustration of amacrocell arranged in accordance with an example of the presentinvention;

FIG. 8 shows a schematic diagram providing an illustration of amacrocell arranged in accordance with an example of the presentinvention;

FIG. 9 shows a schematic diagram providing an illustration of amacrocell arranged in accordance with an example of the presentinvention;

FIG. 10 shows a schematic diagram providing an illustration of amacrocell arranged in accordance with an example of the presentinvention;

FIG. 11 shows a schematic diagram illustrating a femtocell arranged inaccordance with an example of the present invention;

FIG. 12 shows a schematic diagram illustrating a macrocell and atelevision receiver arranged in accordance with an example of thepresent invention, and

FIG. 13 provides a flow diagram indicating steps of a method accordingto an example of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a table of frequency channels which are currently allocatedin the UK for the broadcast of terrestrial television signals. Asdiscussed above, after 2012 channels 61 to 68 are to be reallocated toother uses which may include mobile communication services such as theproposed Long Term Evolution (LTE) fourth generation mobilecommunication system. The remaining channels, i.e. channels 39 to 60,are expected to remain reserved for television broadcast. However, dueto the fact that the frequencies associated with channels 53 to 60 areadjacent in the frequency spectrum to the frequencies associated withchannels 61 to 68, it is possible that use of channels 61 to 68 for LTEcommunications will interfere with the reception of television contentbroadcast on channels 53 to 60. This is explained further with referenceto FIG. 2.

FIG. 2 shows a schematic diagram illustrating various parts of aconventional television 1, which includes a receiver 2. For clarity,various parts of the television have been omitted such as amplifierstages and so on but these parts are known in the art. The receiver 2includes an antenna 3 that intercepts radio signals broadcast from atelevision transmitter 4 and a tuner 22 which is arranged to filter outall signals apart from those associated with a frequency channel to bereceived by the television 1. For example, with reference to FIG. 1, ifthe television 1 was tuned to receive content broadcast on channel 60,the tuner 22 would be tuned to receive radio signals with a centrefrequency of 786 MHz. After the received television signal has beenfiltered by the tuner 22, a demodulator 23 demodulates the selectedsignal and converts it typically into audio/video information that canbe reproduced by the television 1 as sound and pictures.

A mobile device 5 situated near the television 1 includes atransmitter/receiver unit 6 which receives and transmits radiocommunication signals to and from a base station 7 via an antenna 8.

If the frequency band on which the mobile device 5 is transmitting theradio communication signals is sufficiently close to the frequency bandthat the tuner 22 in the receiver 2 is tuned to receive (for examplechannel 61 with a centre frequency of 794 MHz), the radio signals fromthe mobile device 5 may not be filtered out by the tuner 22 and mayinterfere with the signals to be demodulated by the demodulator 23. Thismay arise because television receivers are typically very sensitive soas to be able to receive signals broadcast from transmitters that are upto several tens of kilometers away. Therefore, radio signals transmittedfrom the mobile device in the vicinity of the television may penetratethe television itself, thus “bypassing” the tuner 22, and even perhapsentering the demodulator 23 directly.

In some examples interference might be expected to occur if the mobiledevice or base station is up to 3 to 10 meters from the televisionreceiver. However, the extent of the interference will also depend onfactors including how close to the frequency band the mobile device andbase station are transmitting with respect to the frequency band thatthe television receiver is receiving and the extent of any filtering andscreening within the TV and tuner.

Interference with the signals to be demodulated by the demodulator 23will result in a reduction in the quality of the sound and picturereproduced by the television 1.

LTE Mobile Communications

FIG. 3 a shows a schematic diagram illustrating a first and secondversion of a potential allocation of the frequency spectrum in the 790to 862 MHz frequency band. In 2009 the UK regulatory body OFCOM proposedto widen an originally planned cleared upper frequency band (the socalled “Digital Dividend”) which will become available after digitalswitchover is completed in 2012/2013. This will allow the UK to alignitself to a proposed pan-European band of 790-862 MHz which can be usedfor mobile broadband and other services after digital switchover.

Specifically, FIG. 3 a shows the 2009 OFCOM proposal to move PMSE(Programme making & Special Events) from channel 69 down to 38 and theplan to re-locate channels 61 and 62 to lower frequency channels such as39 and 40. Additionally, PMSE access to TV bands 61-68 on an interleavedbasis will no longer be permitted by end 2012/early 2013.

FIG. 3 b provides a schematic diagram illustrating a possibleimplementation of the LTE UHF frequency band which could be used by LTEbase stations and mobile devices such as the mobile device and basestation shown in FIG. 2.

The frequencies between 790 and 791 MHz provide a 1 MHz guard band 301.The frequencies between 791 to 821 MHz are allocated for downlink datatransmission (i.e. transmission of data from an LTE base station to LTEmobile devices) and define a downlink spectrum 302. The downlinkspectrum 302 is divided into six blocks (i.e. frequency sub-channels) of5 MHz width. A duplex gap 303 of 11 MHz is provided between thefrequencies of 821 to 832 MHz. The frequencies between 832 MHz to 862MHz are allocated for uplink data transmission (i.e. transmission ofdata from LTE mobile devices to the LTE base station) and define anuplink spectrum 304. Like the downlink spectrum 302, the uplink spectrumis also divided into six blocks (i.e. frequency sub-channels) of 5 MHzwidth. Mobile communication systems, such as LTE, are designed so thatcomponents such as the base station can adapt the frequency band invarious ways. This can include limiting or completely suppressing thetransmission of the radio communication signals on individual blocks ofthe uplink and downlink spectrum and varying the width of the blocks.

Should the LTE UHF frequency band shown in FIG. 3 b be implementedwithout any adaptation, it has been identified that television contentbroadcast on frequency channels 53 to 60 shown in FIG. 1 would be atrisk from interference from LTE devices and frequency channels 58 to 60would be at a particular risk.

FIG. 4 provides a schematic diagram illustrating some of the differenttypes of cells that can be employed in a typical LTE mobilecommunication network. As with conventional mobile communicationnetworks, a geographical area is divided into a number of differentcells which are served by a base station. Data is transmitted betweenthe base station and the mobile devices via radio communication signalstransmitted for example, in accordance with the communication schemeillustrated in FIG. 3 b. LTE networks may include cells of differentsizes, some of which exist within other larger cells. For example asshown in FIG. 4, a “femtocell” 401 provides short range coverage whichmay be suitable to provide network coverage within a house; a “picocell”402 may provide network coverage within a large building such as anoffice block or apartment block, a “microcell” 403 may provide networkcoverage within a small urban area covering an area from the basestation of a few hundred meters and a “macrocell” 404 may providenetwork coverage to a larger suburban area covering an area from thebase station of up to a few kilometers.

Television Regions

Countries such as the UK are divided into different television broadcastregions. Each television region is typically served by a singletelevision transmitter which broadcasts streams of television content onvarious frequency channels (i.e. the frequency channels shown in thetable of FIG. 1). FIG. 5 provides a map illustrating the distribution ofdigital television transmitters throughout the UK.

For conventional analogue television transmission, a differentaudio/video stream is broadcast on each frequency channel. Thesedifferent audio/video streams are referred to as “television channels”.Examples in the UK include “BBC 1”, “BBC 2” and “Channel 4”. However,for digital television transmissions (such as those using the DVB-Ttransmission scheme) a “multiplex” of content is broadcast on eachfrequency channel which can include multiple audio/video streams alongwith other content such as interactive services, content from theinternet such as web pages and so on. So for example in the UK, both“BBC 1” and “BBC 2” may be broadcast on the same frequency as part of asingle multiplex. For simplicity, the content broadcast on eachfrequency channel is referred to as a “television content stream”. Atelevision content streams is also known as “service” when referring todigital television signals transmitted in accordance with the DVB familyof standards such as DVB-T.

The allocation of each television content stream for transmission on oneof the frequency channels depends on a so-called “channel map”. Thechannel map is defined by network planners and maps each frequencychannel to a television content stream. For example, with reference toFIG. 1, a first television content stream may be transmitted on channel39 (with a centre frequency of 618 MHz) and a second television contentstream may be transmitted on channel 40 (with a centre frequency of 626MHz).

Typically adjacent television transmitters (and thus television regions)are arranged to use a different channel map so that the same televisioncontent stream is broadcast on different parts of the frequency spectrumin adjacent television regions. This is to avoid interference issues atthe boundaries between television regions.

For example, as can be seen from FIG. 5, the television transmitter atKnock More 501 is adjacent to the transmitters at Durris 502 and Angus503. Accordingly, in a simplified example, television content streamstransmitted from these transmitters could include a first televisioncontent stream (M1), a second television content stream (M2), a thirdtelevision content stream (M3), a fourth television content stream (M4),a fifth television content stream (M5), a sixth television contentstream (M6) and a seventh television content stream (M7).

In this example, the channel map for the Knock More transmitter 501, theDurris transmitter 502 and the Angus transmitter 503 could be arrangedas set out in Table 1 below:

TABLE 1 Television Frequency channel Frequency channel Frequency channelcontent from Knock More from Durris from Angus M1 60 53 43 M2 59 39 44M3 58 40 45 M4 51 41 46 M5 50 42 47 M6 49 43 48 M7 48 44 49

As can be seen by comparing Table 1 with the table shown in FIG. 1, fromthe Knock More transmitter 501 three television content streams arebroadcast on frequency channels that are at risk of being affected byLTE transmissions transmitted using the scheme indicated in FIG. 3 b,namely M1 on channel 60 (786 MHz), M2 on channel 59 (778 MHz) and M3 onchannel 58 (770 MHz). From the Durris transmitter 502 one televisioncontent stream is broadcast on a frequency channel that is at risk ofbeing affected by LTE transmissions, namely M1 on channel 53 (730 MHz).From the Angus transmitter 503 there are no television content streamsbroadcast on frequency channels at risk of LTE interference.

As Table 1 shows, the effect of LTE transmissions will vary fromtelevision region to television region. Specifically, televisionreceivers located in television regions provided by the Knock More andDurris transmitter will potentially experience interference if a LTEmobile device and/or base station is situated in the vicinity of thetelevision receiver. On the other hand television receivers located inthe television region provided by the Angus transmitter will not beaffected because there are no television channel streams broadcast onat-risk frequency channels.

As will be explained below, this variation can be exploited to optimisesystems which aim to reduce the interference caused by the transmissionof LTE radio communication signals.

LTE Mobile Communication Network

FIG. 6 shows a schematic diagram illustrating part of an LTE mobilecommunication network. In this example, the LTE mobile communicationnetwork comprises a plurality of macrocells 601 which each include a LTEbase station 602 which communicates data to and from a number of LTEmobile devices 603 via radio communication signals. Each LTE basestation 602 is connected to the LTE core network 605 via a link 607. Thecore network 605 provides centralised network functionality such ascommunicating data between base stations, tracking the mobility ofmobile devices, providing access control and so on. The LTE basestations generally control how the mobile devices communicate data. Forexample, they can control the uplink and downlink frequencies (i.e. thefrequency channel on which data is transmitted from the base station tothe mobile devices and the frequency channel on which data istransmitted from the mobile devices to the base station). Moreover, thebase stations are typically operable to control the exact frequencysub-channel within the uplink channel on which the mobile devicestransmit data.

The plurality of macrocells 601 shown in FIG. 6 are located within atelevision region 604 (for example a geographical area covered by one ofthe transmitters discussed in relation to FIG. 5). As will beunderstood, the entire LTE mobile communication network is likely to bespread over several television regions. In any case, televisionreceivers situated within the television region 604 and in the vicinityof one or more of the base stations and/or mobile devices willpotentially experience interference in the reception of televisioncontent streams on at-risk frequency channels.

As mentioned above, the LTE communication network may also include anumber of smaller cells such as microcells, femtocells or picocells.These cells are provided by a plurality of pico/micro/femto basestations 606. As will be understood from FIG. 5, a macrocell with atypical radius from the base station of 1 to 5 kilometers issignificantly smaller than a typical television region which may have aradius from the television transmitter of several tens of kilometers.

Manual Programming of Macrocell Base Station

FIG. 7 shows a schematic diagram providing a more detailed illustrationof one of the macrocells shown in FIG. 6. The macrocell shown in FIG. 7is arranged in accordance with an example of the invention. Themacrocell base station 602 includes an antenna 602 b for transmittingand receiving radio signals from the mobile devices 603 and a basestation controller 602 a for controlling the transmission of data to andfrom the mobile devices 603. Data is transmitted between the basestation 602 and the mobile devices 603 in accordance with the LTE UHFfrequency band shown in FIG. 3 b. The base station controller 602 aincludes a processor 702 which can adapt how the LTE frequency band isused by generating an adapted LTE frequency band. For example, theprocessor can be arranged to either limit or completely suppress thetransmission of radio communication signals on certain blocks in theuplink or downlink spectrum. Alternately or additionally, the strengthof radio communication signals broadcast on various blocks could belimited. Further still, the period of time during which radiocommunication signals are transmitted on certain blocks could belimited. Further still the frequency width of certain blocks could bereduced.

This adaptation of the LTE frequency band can be performed in dependenceon the channel map of the television region 604 within which themacrocell 601 is situated to reduce interference with television contentbroadcast on the at-risk channels in that particular television region.Examples of this are explained further below.

In one example the base station controller 602 a is connected to a datastore 701 which includes a look-up table that includes details of thechannel map for the television region 604 within which the macrocell islocated. The look-up table can be manually programmed when the basestation 602 is installed, for example via a terminal 702. Depending onthe channel map stored in the look-up table, the processor 702 can thenbe arranged to adapt the transmission of data to and from the mobiledevices 603 to ensure that any interference caused by LTE transmissionis reduced by adapting the LTE frequency band as described above.

For example, in the simplified example explained with reference to FIG.5, assuming that the television region is provided by television signalsfrom the Angus television transmitter, as can be seen from Table 1, noneof the television content streams are broadcast on frequency channelswhich are likely to be affected by interference from LTE transmissions.Accordingly, the look-up table stored in the data store 701 wouldindicate that there is no television content being broadcast on an atrisk channels therefore the base station 602 is free to permit thetransmission of LTE radio communication signals to and from mobiledevices on the entire downlink spectrum 302 and the entire uplinkspectrum 304 and thus the processor need not adapt the LTE frequencyband in any way.

On the other hand, if the television region is provided by televisionsignals from the Knock More television transmitter, as explained aboveat least three of the television content streams are broadcast onfrequency channels that are particularly at risk from interference fromLTE radio communication signals. Accordingly, the processor 702, afterretrieving the channel map from the look-up table in the data store, maybe arranged to limit or completely suppress any LTE transmissions on allblocks of the downlink spectrum 302 and all blocks of the uplinkspectrum 304 of LTE frequency band. In this case, the base station couldbe arranged to allow LTE radio communication signals to be transmittedto and from the mobile devices 603 on alternative sections of thefrequency spectrum which have been allocated for LTE transmissions.Alternatively the processor may be operable to block all but the highestfrequency blocks from the downlink spectrum 302 and the uplink spectrum304 and reduce the width of these blocks. Furthermore the processor maybe operable to reduce, the blocks from a frequency width of 5 MHz to,for example, a width of 1.4 MHz. Alternately or additionally, theprocessor could be operable to adapt a maximum strength of the radiocommunication signals broadcast on various blocks. Further still, theprocessor could define a reduced period of time during which radiocommunication signals are transmitted on certain blocks.

In another example, if the television region is provided by televisionsignals from the Durris television transmitter, as explained above, onlyone of the television content streams is broadcast on a frequencychannel which is at risk from LTE transmissions. Moreover, thisfrequency channel is at the furthest end of the group of channels thatare at risk from interference from LTE radio commutation signals. Inthis case, the processor 702, after retrieving the channel map from thelook-up table in the data store, may be arranged to limit or completelysuppress downlink transmissions in the lower frequency downlink blocksof the downlink spectrum 302. This could be, for example, the threelowest frequency blocks (i.e. 791 to 796 MHz, 796 to 801 MHz and 801 to806 MHz).

Location Based Programming of Macrocell Base Station

FIG. 8 provides a schematic diagram illustrating an example of amacrocell arranged in accordance with another example of the invention.The macrocell shown in FIG. 8 is the same as that shown in FIG. 7 exceptthat rather than a terminal for manually programming the channel map forthe television region 604 within which the macrocell is located, thebase station controller 602 a is connected to a positioning unit 801which is arranged to determine the geographical position of the basestation 602. The positioning unit 801 can be any suitable means forindependently determining the position of the base station 602 such as aglobal positioning system (GPS) unit or a unit based on the Galileosatellite navigation system. In some examples, to improve sensitivity(for example locations where there is no line of sight to a satellite),assisted GPS (AGPS) could be used.

In this example, the look-up table stored in the data store 701 containsa list of the geographical location of all the relevant televisionregions along with the channel map associated with each televisionregion. When the positioning unit 801 identifies the position of thebase station 602, the base station controller 602 a is arranged toaccess the look-up table stored in the data store 701 to determine whichtelevision region the base station is in and the channel map associatedwith that television region. The processor 702 in the base stationcontroller 602 a may then generate the adapted LTE frequency band independence on the channel map as described above.

Macrocell Base Station Programming of Femtocell

FIG. 9 provides a schematic diagram illustrating an example of amacrocell arranged in accordance with another example of the invention.FIG. 9 shows a femtocell 901 which is provided by a femtocell basestation 606. As explained above, the femtocell 901 is effectively ashort range LTE cell provided by the femtocell base station 606. Thefemtocell base station 606 is connected to the LTE core network by alink 904 which is typically provided by a domestic ADSL link. Thefemtocell is arranged in correspondence with the macrocell 601 in thatit includes a data store 902 in which is contained a look-up table ofthe location of all relevant television regions along with correspondingchannel maps, and a positioning unit 903 to determine the location ofthe femtocell base station 606. When the positioning unit 903 identifiesthe position of the femtocell base station 606, the femtocell basestation 606 is arranged to access the look-up table stored in the datastore 902 to determine which television region the femtocell basestation 606 is located in and the channel map associated with thattelevision region. The femtocell base station 606 may then adapt the LTEfrequency band in dependence on the channel map as described above.

User Defined Location Information

FIG. 10 provides a schematic diagram illustrating an example of amacrocell arranged in accordance with another example of the invention.In some situations it may be impractical or undesirable to require thatthe femtocell 606 includes its own data store providing the look-uptable of the various channel maps. Accordingly, in the example shown inFIG. 10, the macrocell base station controller 602 a is arranged todetermine the adapted LTE frequency band as described above. FIG. 10shows the positioning unit 801 which determines the relevant channel mapby identifying the location of the base station. However, it will beappreciated that in this example the channel map could be provided bymanually inputting it to the base station as explained with reference toFIG. 7.

In any case, once the macrocell base station 602 has generated anadapted LTE frequency band in accordance with the identified channel mapas described above, the macrocell base station 602 transmits LTEfrequency band adaptation information to the femtocell base station 606.The femtocell base station 606 is then arranged to adapt the LTEfrequency band accordingly. In some LTE mobile communication networks,femtocell base stations are arranged to communicate with the macrocellbase stations in order to avoid adjacent base station interferenceissues. Thus, a communication channel already exists which will permit afemtocell to manage the bandwidth of either or both of the LTE uplink ordownlink channel bandwidths.

As will be understood, the technique illustrated in FIG. 10 can beapplied to any LTE base station situated within the cell of another LTEbase station. For example a macrocell base station could communicate theLTE frequency band adaptation information to any of a femtocell,picocell or microcell base station, a microcell base station couldcommunicate LTE frequency band adaptation information to a femtocell ora picocell base station, and so on.

Location Input by User to Femtocell

FIG. 11 provides a schematic diagram illustrating a femtocell arrangedin accordance with another example of the present invention.

LTE femtocell base stations are typically intended to be installed by auser in a home environment by connecting the femtocell base station 606to the LTE core network via a communication link such as an ADSL line.The femtocell 901 is then established in the user's home providing LTEnetwork coverage. As before, it is desirable to provide the femtocellbase station with an adapted LTE frequency band in order to reduce alikelihood of interfering with television content streams beingbroadcast on at-risk channel frequencies.

In order to reduce the complexity of femtocell base station 606, ratherthan providing it with a data storage unit including a look-up table,means can be provided which enable the user to send location informationfrom the femtocell base station 606 back to the LTE core network 605 viathe link 904. This location information is then received at the LTE corenetwork 605 which determines the television region within which thefemtocell is located based on the location information by identifyingthe frequency channel plan associated with that television region frominformation stored in a data store 111. An appropriate adapted LTEfrequency band can then be determined and transmitted back to thefemtocell base station 606. The femtocell base station then implementsthe adapted LTE frequency band.

In some examples the location information can be an area code such as aUK “post code” (typically a seven letter alpha-numeric code thatuniquely identifies a geographical regions in the UK). In otherexamples, the location information could be specific postal addressinformation identifying a street or building in which the femtocell islocated. In further examples the information could be longitude andlatitude derived manually by the user from a map or from a positioningsystem.

In some examples the user can input the location information directlyvia an interface 110 on the femtocell base station. In other examples,when the user installs the femtocell base station, they may send a textmessage (such as a short message service (SMS) message) including thelocation information from the mobile device 603 to the femtocell basestation 606. The femtocell base station 606 then sends the text messageincluding the location information to the LTE core network as describedabove. In order to encourage the user to enter the location information,in some examples the femtocell base station 606 can be arranged toprovide reduced functionality until the location information isprovided.

In some examples specific channel map information can be provided by a“teletext” service (i.e. a text based information service which isincluded in a content stream broadcast in a particular televisionregion). The teletext service may be provided by a MHEG (Multimedia andHypermedia Experts Group) application or a Java application. In oneexample a user may access a specific teletext page to access channel mapinformation or a coded representation of the channel map. In someexamples this page may include a specific code to send by a text messageas discussed above. In some examples, at each television transmitterthere may be local insertion of a transmitter-specific teletext pagewith information representing the channel map. (teletext=data service,could be an MHEG or Java application)

In Line Filter on Television Receiver

FIG. 12 provides a schematic diagram illustrating another example of theinvention. In order to further reduce any interference experienced at atelevision receiver due to the transmission of LTE radio communicationsignals transmitted to and from the macrocell base station 602 and theplurality of mobile devices, a television receiver such as a television121 can be fitted with an inline filter 123 on an aerial 122. In oneexample the inline filter 123 comprises a band pass filter arranged tofilter frequency bands on which the LTE radio communication signals arebeing transmitted. With reference to FIGS. 1 and 3, the inline filter123 could be arranged to filter frequencies between 794 MHz to 850 MHz(i.e. frequency channels 61 to 68). This arrangement can reduce theextent to which the LTE frequency band need be adapted to reduce theinterference caused.

FIG. 13 provides a flow diagram indicating steps of a method accordingto an example of the present invention. At step S101 a base stationidentifies the channel map and at step S102 the base station adapts atransmission of radio communication signals to and from mobile devicesin accordance with the channel map.

Various modifications can be made to the present invention. For example,the above examples of the invention have been described in terms of LTEcommunications networks that communicate radio communication signals inaccordance with the UHF spectrum shown in FIG. 3 b and televisioncontent streams which are broadcast on the frequency channels indicatedin FIG. 1. This results in a spectrum in which the television contentstreams are broadcast on a first set of frequency channels and the LTEradio communication signals are broadcast on an adjacent set offrequency channels. However, the concept of identifying a channel map todetermine if or how a mobile communication spectrum is arranged could beapplied to frequency spectrum allocations which differ from this. Forexample, the frequency channels on which the television content streamsare broadcast could be intermixed with the frequency channels on whichthe mobile radio communication signals are transmitted.

Furthermore, although the invention has been explained mainly withreference to LTE mobile communication systems, the invention would beequally applicable to other mobile communication systems known in theart such as UMTS, GSM, CDMA2000 and so on.

The invention claimed is:
 1. A method of reducing interference toreception of streams of television content received at a televisionreceiver, each of the streams of television content being transmitted onone of a plurality of frequency channels in accordance with a channelmap, the channel map defining for each of a plurality of televisionregions a mapping of each stream of television content onto one of theplurality of frequency channels on which the stream of televisioncontent is transmitted, the interference being caused by a base stationtransmitting data to or receiving data from one or more mobile devicesvia radio communication signals in a vicinity of the televisionreceiver, the radio communication signals being transmitted from thebase station to the one or more mobile devices via a downlink frequencychannel or transmitted from the one or more mobile devices to the basestation via an uplink frequency channel, the uplink frequency channeland the downlink frequency channel being divided into frequencysub-channels, the method comprising: identifying a geographical locationof the base station; determining from the geographical location of thebase station a television region in which the base station is located byreferring to a television region map indicating a geographicaldistribution of television regions; identifying the channel mapassociated with the television region by referring to informationindicating the channel map associated with the television region; anddepending on whether the channel map indicates that at least one of thefrequency channels is adjacent to one of the uplink frequency channel orthe downlink frequency channel, adapting the transmission of the radiocommunication signals between the base station and the one or moremobile devices in accordance with the identified channel map to reduceinterference at the television receiver by selectively limiting orblocking one or more of the frequency sub-channels of the uplinkfrequency channel and/or the downlink frequency channel.
 2. A methodaccording to claim 1, wherein the identifying of the channel mapcomprises identifying the channel map from data manually entered into adata store connected to the base station.
 3. A method according to claim2, wherein the identifying of the location comprises receiving locationinformation from a positioning unit connected to the base station.
 4. Amethod according to claim 2, wherein the identifying of the locationcomprises receiving location information from one of the one or moremobile devices.
 5. A method according to claim 4, wherein the locationinformation is input to one of the one or more mobile devices by a userand transmitted to the base station as a text message.
 6. A methodaccording to claim 1, further comprising transmitting adaptationinformation indicating which of the frequency sub-channels have beenselectively limited and/or blocked and an extent to which the frequencysub-channels have been selectively limited or blocked to a second basestation, wherein the second base station communicates data with one ormore mobile devices via radio communication signals in accordance withthe selective limiting or blocking of the frequency sub-channelsindicated in the adaptation information.
 7. A base station fortransmitting data to and receiving data from one or more mobile devicesvia radio communication signals, wherein the base station is operable:to transmit the radio communication signals to the one or more mobiledevices via a downlink frequency channel; to control the one or moremobile devices to transmit the radio communication signals to the basestation via an uplink frequency channel, the uplink frequency channeland the downlink frequency channel being divided into frequencysub-channels; to identify a geographical location of the base station;to determine from the geographical location of the base station atelevision region in which the base station is located by referring to atelevision region map indicating a geographical distribution oftelevision regions; to identify a channel map associated with thetelevision region by referring to information indicating the channel mapassociated with the television region, the channel map defining for eachof a plurality of television regions a mapping of each stream oftelevision content onto one of a plurality of frequency channels onwhich the stream of television content is transmitted; and depending onwhether the channel map indicates that at least one of the frequencychannels is adjacent to one of the uplink frequency channel or thedownlink frequency channel, to adapt the transmission of the radiocommunication signals from the base station to the one or more mobiledevices, and to adapt a transmission of the radio communication signalstransmitted from the one or more mobile devices in accordance with thechannel map by selectively limiting or blocking one or more of thefrequency sub-channels of the uplink frequency channel and/or thedownlink frequency channel in accordance with the channel map to reduceinterference to the reception of the streams of television contentreceived at a television receiver in a vicinity of the base station andthe one or more mobile devices.
 8. A base station according to claim 7,wherein the base station comprises a data store in which is stored datacorresponding to the channel map and means for enabling the channel mapto be manually input to the data store.
 9. A base station according toclaim 7, further comprising a means for determining location informationaccording to a positioning unit connected to the base station, thepositioning unit being operable to determine a location of the basestation.
 10. A base station according to claim 7, further comprising ameans for the determining location information according to a means forenabling a user to manually enter the location information into the basestation.
 11. A base station according to claim 7, operable to transmitadaptation information indicating which of the sub-channels has beenselectively limited and/or blocked and an extent to which thesub-channels have been selectively limited and/or blocked to a secondbase station, enabling the second base station to communicate data withone or more mobile devices via radio communication signals in accordancewith the adaptation information.
 12. A network comprising a plurality ofbase stations according to claim
 7. 13. A system comprising atransmitter station and a television receiver, the transmitter stationbeing configured: to transmit the radio communication signals to the oneor more mobile devices via a downlink frequency channel; to control theone or more mobile devices to transmit the radio communication signalsto the base station via an uplink frequency channel, the uplinkfrequency channel and the downlink frequency channel being divided intofrequency sub-channels; to identify a geographical location in which thetransmitter is located; to determine from the geographical location ofthe transmitter station a television region in which the transmitted islocated by referring to a television region map indicating ageographical distribution of television regions; to identify a channelmap associated with the television region by referring to informationindicating the channel map associated with the television region, thechannel map defining for the determined television region a mapping ofeach stream of television content onto one of a plurality of frequencychannels on which the stream of television content is transmitted; anddepending on whether the channel map indicates that at least one of thefrequency channels is adjacent to one of the uplink frequency channel orthe downlink frequency channel, to adapt the transmission of the radiocommunication signals from to the one or more mobile devices, and toadapt a transmission of the radio communication signals transmitted fromthe one or more mobile devices in accordance with the channel map byselectively limiting or blocking one or more of the frequencysub-channels of the uplink frequency channel and/or the downlinkfrequency channel in accordance with the channel map to reduceinterference to the reception of the streams of television contentreceived at the television receiver in a vicinity of the transmitterstation and the one or more mobile devices; and the television receivercomprising an aerial for receiving the streams of television contenttransmitted on the frequency channels, wherein the aerial includes afilter arranged to attenuate the radio communication signalscommunicated between the transmitter station and the one or more mobiledevices.
 14. An apparatus for reducing interference to reception ofstreams of television content received at a television receiver, each ofthe streams of television content being transmitted on one of aplurality of frequency channels in accordance with a channel map, thechannel map defining for each of a plurality of television regions amapping of each stream of television content onto one of the pluralityof frequency channels on which the stream of television content istransmitted, the interference being caused by a base stationtransmitting data to or receiving data from one or more mobile devicesvia radio communication signals in a vicinity of the televisionreceiver, the radio communication signals being transmitted from thebase station to the one or more mobile devices via a downlink frequencychannel or transmitted from the one or more mobile devices to the basestation via an uplink frequency channel, the uplink frequency channeland the downlink frequency channel being divided into frequencysub-channels, the apparatus comprising: means for identifying ageographical location of the base station; means for determining fromthe geographical location of the base station a television region inwhich the base station is located by referring to a television regionmap indicating a geographical distribution of television regions; meansfor identifying the channel map associated with the television region byreferring to information indicating the channel map associated with thetelevision region; and means for adapting the transmission of the radiocommunication signals between the base station and the one or moremobile devices, depending on whether the channel map indicates that atleast one of the frequency channels is adjacent to one of the uplinkfrequency channel or the downlink frequency channel, in accordance withthe identified channel map to reduce interference at the televisionreceiver by selectively limiting or blocking one or more of thefrequency sub-channels of the uplink frequency channel and/or thedownlink frequency channel.